1) What is the meaning of the percentage, or I might ask, what means 100% zoom in the canvas positioner?? What does this number actually express? Is it related to the (my) screen resolution or is it unrelated?

The above question comes from the next question:
2) I would like to know how much this number has to be in order to view my painting at the exact size (*putting a ruler on my screen*) it would be on paper if printed out.
Now, I read and think I understand, a lot about ppi and dpi and printers etc pp etc.... I know about these things, but they are seemingly (?) unrelated to my question. I usually set my canvas in the tab "print size" to the size I would like it to be able to be printed out in good quality and also, set it to 300 dpi. (But I guess this is beside the point).

Again, how much do I have to zoom in or out so that I see the size on screen as if printed?? I am aware of the fact that if my painting should be printed out bigger than my screen, I would not see it all, of course.

I carefully did a lot of attempts with keywords and such to look through the whole forum and did not find any answers. Please - do not try to go over the dpi-question (unless inasmuch it is related to the above question), I think I found a lot of resources & posts related to dpi etc.